Community antenna television (“CATV”) networks have been used for more then four decades to deliver television programming to a large number of subscribers. Increasingly, CATV networks are used by providers to provide data services to subscribers. For example, cable modems used in a broadband cable modem termination system (“CMTS”) are capable of transmitting and receiving Internet data using the Data Over Cable Service Interface Specification (“DOCSIS”) protocol. DOCSIS provides a standard that allows network devices made by different vendors to communication with one another.
Similar to DOCSIS, which is administered by Cable Television Laboratories, Inc. (CableLabs®), “PacketCable™ is a CableLabs-led initiative aimed at developing interoperable interface specifications for delivering advanced, real-time multimedia services over two-way cable plant. Built on top of the industry's highly successful cable modem infrastructure, PacketCable networks will use Internet protocol (IP) technology to enable a wide range of multimedia services, such as IP telephony, multimedia conferencing, interactive gaming, and general multimedia applications.” See www.packetcable.com. DOCSIS and PacketCable are protocol standards known in the art and do not require further discussion of the basic functioning thereof. However, it will be appreciated that, although DOCSIS and PacketCable are currently considered industry standards, other protocol standards may become predominant over time. Thus, for purposes of discussion herein, DOCSIS may be generically referred to as a ‘data protocol’ and PacketCable as a ‘multimedia protocol.’
A multimedia protocol can be used in conjunction with the Internet to provide services, such as, for example, a voice call that emulates a plain old telephone service (“POTS”) telephone call. Another service common in the pre-existing Telecommunication marketplace is DS1 or E1 multi-channel transport service. Several vendors have developed devices that allow multi-channel TDM services, such as DS1 service or E1 service, to be transported over packet-switched networks, such as the Internet. These devices are known in the art as Integrated Access Devices (“IAD”). As shown in FIG. 1, a public branch exchange (“PBX”) 2 is often served by a DS1 link 4, DS1 technology being known in the art. The DS1 4 and PBX 2 arrangement may typically be used to support multiple call circuits to an office building, for example. IAD 6 provides an interface between the DS1 with its TDM formatting and a cable modem 8 with its packet-switched technology. Thus, the 24 channels of DS1 4 are formatted by IAD 6 before being transported by modem 8 to an access multiplexer (e.g., a CMTS 10). Network 12 between modem 8 and CMTS 10 represent a coaxial or HFC network, for example.
After data contained in the formatted 24 channels has been transported across network 14, which is preferably the Internet or a similar packet-switched network, IAD 16 removes the formatting performed at IAD 6. The 24 channel data streams are then provided to a conventional telephony central office, which routes calls that originated at PBX 2 to a POTS network. Thus, conventional POTS telephony calls placed (or received) from/at PBX 2 are packaged and formatted at IAD 6 before being transported across network 14 before being unformatted/unpackaged at IAD 16. This process is typically referred to in the art as ‘transport’ because the continuous TDM digital data stream bearing the call traffic between central office 18 and PBX 2 is essentially packed into IP packets at one end and sent to the other end, where the continuous digital data stream is essentially ‘unpacked’ from the packetized stream and reformed into the original continuous data stream that existed before being converted.
While transport of the 24 DS1 channels provides a means for an operator to provide traditional telecommunication services over a packetized cable network, thus providing competition to the traditional telephone companies, implementation of the system in FIG. 1 can result in inefficient use of cable network bandwidth. For example, since transport of signals provides at the end point the data stream that was injected at the starting point, a caller's audio silence still results in bandwidth being allocated to the call's channel. Even though there is no information being transmitted or received, and thus no bandwidth needed to carry useful information, the same amount of bandwidth between IAD 6 and IAD 16 is reserved as is used when the DS1 channel is carrying dense audio information. This is bandwidth that is not available for allocation to other users over network 12 and packet-switched network 14. Furthermore, IADs 6 and 16 only package the voice call information into a format for transporting between modem 8 and CMTS and across the packet-switched network 14 to the other IAD. Accordingly, call processing features are not performed by IADs, and must be performed by legacy POTS network switches. Alternatively, the operator must purchase additional equipment that will translate signals at a PBX DS1 into VoIP signals.
Thus, there is a need in the art for a method and system for using a cable data network and the internet to support multi-channel telecommunications services, as well as other multimedia signals, that minimize bandwidth waste and minimize the cost to provide these services using industry preferred networking and VoIP technologies.